What's the difference....

There is very little difference between those words.

"Tour" is the most distinct of them. Unlike the others, "tour" suggests a visit to multiple locations. The other words could mean that too, but they don't have to.

"Voyage" is often used to describe a trip by sea, but it doesn't have to.

"Journey" is often used metaphorically; it can be used if you want to compare a process or passage of time to a physical trip (e.g. "a spiritual journey"), but it doesn't have to.

Still, in many cases those words could be used as synonyms for each other.

These posts asking for translation more rightly belong in the English forum.